


An Equation Heaven Sent

by guileheroine



Category: Avatar: The Last Airbender
Genre: Alternate Universe - Merpeople, Crushes, Drunken Shenanigans, F/M, Friendship, Gen, Hurt/Comfort, M/M, Multi, OT3, Poetry, Pre-Poly, Sickfic, Slice of Life
Language: English
Status: In-Progress
Published: 2019-05-18
Updated: 2020-02-14
Packaged: 2020-03-07 10:23:26
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 3
Words: 3,876
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/18871279
Author URL: https://archiveofourown.org/users/guileheroine/pseuds/guileheroine
Summary: A ficlet collection centring on Aang, Katara and Zuko, usually together.





	1. Sunshine

**Author's Note:**

> Zuko relaxes with his best friends at their favourite hideout in all Four Oceans.
> 
> A little Zutaraang ficlet for Mermay!

The sun glinted off the smooth stones around Katara’s neck when she arched it to let the light drench her. An easy smile graced her face, although the sheer brightness of the light forced a slight pucker in her brow. The last time Zuko had gone down south, he took Aang and they scaled the caverns off the edge of Ember Island for several hours to find the larimer, thinking how perfectly it would complement the refracting blue of Katara’s scales. The mineral was a rare find these days, most of it hoarded in the heavily guarded treasury chests of his father’s court, or else in the covetous clutch of the mer-chants that flowed daily now between the Four Oceans. It wasn’t hard for Zuko to float amongst the traffic unnoticed, to waters he was technically unwelcome to, though he didn’t yet dare breach the stony reef complex of the palace again. 

 

During the height of summer, however, he preferred to linger in kinder latitudes with his best friends. Their company was especially welcome after a trip back to the tropics, even if it had been well worth it this time, because Katara squealed in delight once they presented her with the gems. 

 

“Zuko, this kind of stinks,” Aang had coughed in a flurry of bubbles when they were down by the island searching. Volcanic vents hissed in criss-crosses all along the bed in that region of Zuko’s homesea, part of the reason why precious minerals could actually still be found there. Impervious to the heat if not the smell, Aang got over it quickly, simply bending the pockets of sulfur out of the water before him. He entertained himself by crouching above the vents, so they puffed him several metres up until he broke the surface with a hearty laugh. Zuko had no idea why that could be so thrilling for someone who was no longer a child, and more importantly, could already airbend.

 

Zuko had ground his teeth. “ _Aang_. Be careful!” They would probably both be thrown into the fissures together if they were caught here, since fraternising with the Avatar was what got Zuko banished from his father’s kingdom in the first place, all those years ago. He told Aang as much, sparing no grisly details.

 

Aang shrugged and told him there was no one he’d rather die in a volcano with, though he curled his tail close afterwards and put new eyes on the search. The steam that heated the water, Zuko was appalled to find, was not from the vents but his own ears.

 

Yue Bay was temperate, though not as clear as the tropics. Presently Zuko gazed again out to where Katara lay in the shallows. The sun came down like a spotlight on her, drawing his eyes. The brilliance of it on her skin, on her wet hair, was irresistible. When Katara sunbathed, it brought out the freckles of pale silver on her shoulder until they bled together like beading water. She took a second to wring it out before adjusting her position against a rock, pulling herself up. A surreptitious cock of the head in his direction, before she settled more comfortably.

 

But the midday sun forced Zuko back like a staying hand, mixing with the tendrils of a budding headache that stretched all the way down to the tip of his tail fin. He lay quiet and heavy in the shade of the cave. He was nodding against his chest when the distant tinkle of Katara’s laugh carrying over pulled his consciousness back out to the water.

 

The pool around Katara undulated with the lively, telltale rhythm of his familiar movements - Aang had returned from his (apparently fruitless) stakeout of the unagi’s cave. Zuko had told him it wouldn’t couldn’t come out on such a hot day, but whatever, what did he know - Aang decided to try his luck anyway.

Suddenly Aang leapt out and over Katara’s head, Momo gliding alongside.

 

The majestic arc of his body seemed never to end. His tail was definitely longer than Zuko’s, if you counted the wispy fins - had been for several years, but it never failed to surprise him with the sprightly way Aang moved. His bright silken fins fluttered in the air, masts on a speedy little boat. Their colour made Zuko wish for sunset. When Aang alighted on the rock behind Katara’s head, almost panting, he quickly re-knotted the band that protected his bare head from the sun, before shielding his eyes as he gazed towards the cave. The web of his arm spread like a wing when he lifted it.

 

“Nah, no luck,” he called to Zuko, referring to the unagi. Momo dove a repeated a circle around the tapered end of Katara’s tail, light falling through his translucent fins in a similar fashion. Aang had adopted him many moons ago, the sole survivor of a shoal of flying fish decimated by a vicious electric hunter.

 

Zuko tried to give Aang a look that said _I told you so_ , but he wasn’t sure if he could read an expression that fine from over there. He wasn’t looking anyway, he had his head bowed now to hear whatever Katara was telling him.

 

Katara leaned her own head back into Aang’s waiting hands. Zuko watched the play of Aang’s fingers along the shell of her ear as he scooped her hair back. They would have been such a welcome sensation on his own aching head. He could tell that she relished the touch, together with the weather that made her dozy. Even in the freezing polar seas where she came from they enjoyed brilliant sunlight.

 

Sokka was up there on some ice fishing trip right now. He had explained when inviting Zuko how it involved cornering your prey between yourself and the frozen ceiling of the sea. Zuko remembered Suki rolling herself in a vat of blubber before they swam up, once Sokka had finally convinced her to come along. For himself, he realised he preferred to be down here with Aang and Katara. Just Aang and Katara.

 

This place was, in fact, a special sanctuary of theirs. Yue Bay tended to be the perfect place for the three of them to relax together, even if it was just a little cool for Zuko in the winter, or a little warm for Katara in the summer, or fell short of Aang’s ideal number of heights to dive from. (Zuko had visited the long cascades that made up the home of his tribe once, where they plunged from the cliffs as lightly as if they were just dipping their fins.)

 

They had discovered this cavern during a storm on the way to some gathering. Despite Katara’s best efforts to calm them, the huge grey waves had lashed at them until there was nothing to do except seek shelter, above or below. In the end, they had been forced to spend hours waiting for the tempest to pass, but they spent it better than they could have expected. Zuko warmed the water that crept in, and they plucked from the sand the gobies and other tiny creatures thrown wayward by the gales, eating them or flicking them back, while they talked about their deepest fears.

 

He had heard Toph sputter something about ‘The Cave of Three Lovers’ once. Toph had a name for every cave and burrow she knew, hailing as she did from fathomless depths Zuko could hardly imagine; navigating those deep trenches sightless better than anyone. She wiggled away cackling before he could do anything, not that he could do anything except, well, steam. Thank the depths Katara and Aang had been out of earshot.

 

Right now, he was out of earshot of them as they murmured curiously to each other. Katara’s soppy hair was dry and newly braided. Aang palmed the sand to pull out a stringy weed to fasten it in place with. They shared another conspiratorial exchange before turning in Zuko’s direction together and raising their voices.

 

“Your turn!”

 

“What’s the matter, Zuko?”

 

“Don’t you think you could use a tan?”

 

“I think he could use a tan.”

 

“Oh, he could definitely use a tan.”

 

Zuko’s dorsal fin twitched irritably. He could take maybe another minute of this in his state. He prepared to swim out, knowing when he’d been given no choice.


	2. An Ode to Master Katara

**Notes for the Chapter:**

> a little thing for Zutaraang Week 2019, for the 'sunlight/moonlight' prompt!

It’s unclear who roped who into this. It may have been Aang (let’s face it - it probably was), who goaded Zuko into acknowledging that he’d overworked on his stupid address for tomorrow’s stupid council to the point of complete inefficiency; and there was nothing more to do about it whether he remained at his desk or not. It might actually have been Zuko, who doubled Aang’s request for drinks the second the porter delivered his order from the brewery down the street. 

 

It’s also horrifically unclear whether the deal they’re going to pitch to the Southern Water Tribe’s envoy for trade tomorrow is going to be a total non-starter. Aang, Zuko, and the rest of the council have been unable to gain the cooperation of Republic City's ‘burgeoning industrialist class’ (their words) for an agreement to abolish colonial-era tariffs for southern manufactured goods. The Southern Water Tribe, meanwhile, are pretty adamant that - new nation or no - the United Republic’s industries have burgeoned quite enough from all the investment that the Fire Nation had pumped in over the decades; and had threatened to pull fur apparel exports altogether unless the UR cut some of the taxes within three months. 

 

And three months, Zuko and Aang have learnt the hard way, is not nearly enough time to hammer out a satisfying trade deal. Luckily, having learnt this, they’ve also found the fine brew necessary to live with their new knowledge. 

 

Aang thinks as much as he tilts the beer in his hand sideways to scrutinise the seal on the bottom. It swims briefly like a floater before his vision, before he straightens the bottle just fast enough for it not to slosh all over his lungi. Distracted, Zuko throws him a look of vague, irritated warning. 

 

Then he slips right back into deep thought. Miles deep - his free hand clutched on his knee in concentration, muttering vaguely under his breath. Sheepish, Aang takes it as a reminder to call his own fuzzy mind to task.

 

“ _ As sharp as a spider snake’s bite…  _ Her...” He thinks very hard. There’s  _ so  _ much he could say. In his present state the mere thought makes his throat tight, eyes shine. “Her  _ smile  _ like…  _ pure _ ..”

 

What  _ is  _ clear - if little is, at this point in the night - is that tomorrow’s untouchable high point is going to be Katara’s arrival on the Water Tribe delegation boat. No diplomatic disaster could possibly mar that. It almost makes the rest worth it, or at least that’s what they’re telling themselves. That’s what Zuko  _ was  _ telling himself, and telling Aang, prompting Aang to drunkenly declare that they should write Katara a poem; and since then the ensuing pursuit has consumed all of their pretty unstable faculties. 

 

“...Ugh! We’re so close, c’mon, Zuko!” 

 

“I know, I know,” Zuko snaps. “What rhymes with bite -  _ what rhymes with bite  _ -” He keeps repeating, like a riddle that will solve itself if repeated with enough verve.

 

The urgency vibrates between them; Aang’s bottle is forgotten as he stands. This - well, they have to succeed at something tonight, right? And it has to be  _ this _ . That is clearest of all, as Aang finds himself on the precipice of an answer, looking to Zuko searchingly to push him over to victory. Their eyes manage to meet in shared determination. Aang burps and puffs his chest, clearing his throat. “Her tongue is as sharp as a spider snake’s bite, her smile is as pure  _ as  _ -”

 

“Moonlight!”

 

“Sunlight!”

 

“ _ No - _ ”

 

“Wait!”

 

“Moonlight,” Zuko repeats again with grave certainty, cutting quite the contrast from the last half hour, from his general countenance these last few days.

 

But Aang isn’t sure. He rocks on his heels, shrugging. “But, Zuko... don’t you think sunlight’s like… sunnier, though?” Buoyed with enthusiasm from his little light bulb moment, he grasps behind blankly for his bottle.

 

Zuko does the same, his own drink on the patterned rug between his legs. He gives a rapid shake of the head. “No, no. You know - water…” he says slowly, “moon.”

 

_ Oh _ , good point. Aang nods sagely, feeling his own point of view enlightened by the clarity of Zuko’s perception. 

 

But then Zuko’s eyes pop - like a sudden insight has pierced clear into his brain, blistering amongst all the stewing thought. “Didn’t Sokka’s girlfriend turn into the moon?” He grimaces. “That’s kind of weird now,” he says, tasting the thought. “...Sunlight.”

 

Aang deflates. “No, moonlight. You were right, Zuko, it’s gotta be moonlight.” He reseats himself with a sweep of finality. 

 

Zuko gives a sigh, then holds his fist in the air before him. “Think about it. Let’s just think about it.”

 

“Moonlight - that’s how it feels,” Aang says in a heartsick haze, “it’s cool like moonlight.” Katara’s smile settles him, grounds him when he’s given to flight; how else could he say that?

 

When he glances expectantly to Zuko, however, he’s lost in thought again. Aang’s own reflection seems to have spurred him.

 

“Sunlight,” Zuko insists. The feeling in that fist more tender now, clutched - guarded - a little self consciously below his chest. “Like... opening the curtains in a dark room after ages.” Aang catches the impression of a slight daze much like his own. Somehow it just lends more weight to his words.

 

Wow, Zuko really is a poet. And there  _ are a  _ lot of dark rooms in the palace at the Fire Nation, so, like, he would definitely know. But still. Aang’s sure in his gut about this one, in his heart.

 

“I like moonlight.”

 

“Well, I like sunlight.”

 

-

 

Katara unlocks the door to her study here in their Republic City quarters and pushes it open with the weight of her side, heaving a sigh as she drags her feet in. So that meeting was an unmitigated disaster. 

 

She’s exhausted from her trip, and she can’t pretend that this let down just concluded hasn’t added considerably to her dejection. Granted, the Southern Water Tribe delegation weren’t the easiest guests to please, but she hadn’t anticipated that UR Council were going to run into such a dead end trying to negotiate with business here (Katara has a mind to go give them all a dressing down herself, if she knew which fancy club to find them in.) The entire time this afternoon, she had been caught between moments of acute sympathy for Aang, Zuko and the others (and were they -  _ hungover? _ ); and cringing and wincing for her life as they stumbled through the awkward negotiations.

 

She stops - her thought arrested, probably for the best - when she treads on something uneven beneath her thin slippers. She bends to pick the little envelope up. It’s unsealed - the memo paper they have downstairs, gifted to the Avatar’s residence from some new stationer’s, peeking out. 

 

Katara flops on the bed and pulls the square out. Zuko’s hasty scrawl, followed by a couple of lines in Aang’s hand. Both cruder than usual.

 

_ Her head is strong, her hair is long. _

_ She’s sweeter than a lyrelark’s songs _

_ Nothing compares to her bending power  _

_ She makes all the other waterbenders cower _

_ Her mind’s as sharp as a spider snake’s bite _

_ Her smile as pure as sunlight/moonlight _

  
So they  _ are  _ hungover. Katara clutches the paper to her chest, and bursts into laughter. 


	3. Love Stings

**Notes for the Chapter:**

> for @onetruethree for the zutaraang valentine's exchange!

_Where was he?_ Aang drew his hand away from his mouth, cracked his knuckles and shot hot air between his palms. He paced the floor again. Zuko was more than two hours gone. If the secondhand knowledge of desert toxicology he had dug out from the back of his mind, and the books from the Royal library currently strewn over the rug that had corroborated it, were anything to go by, then that didn’t give Katara much time.  **  
**

The seam of the Spirit World hovered in the periphery of his mind’s eye. That would be the last resort.

Aang silently cursed King Kuei’s stupid penchant for exotic creatures and wished he’d be satisfied with pets that befit his own abject (and more importantly,  _harmless_ ) dullness. He breathed and planted his feet firmly on the carpet, soothing himself by imagining the tirade Katara would be spiraling on if their positions were switched. Kuei would be in his chambers with his tail between his legs, not tittering defensively as though poisoning your guests was just another Earth Kingdom tradition. Katara would have shut the door in his face much sooner than Aang had.

He supposed it shouldn’t have been a calming image, but it was familiar and predictable and that made its therapeutic value unmatchable somehow.

Now that he thought about it, it was true: it usually  _was_ the other way around. Katara was the healer here, and Aang - especially in a moment like this - he was as wide-eyed and foolhardy as the day they met, waiting for her sign. 

Suddenly Katara croaked something in her daze, and he rushed to bow over her, as she had him countless times.

“I’m here, Katara.” He gulped. He patted her sweaty forehead. “I’m right here.”

Lucid or not, Katara produced a delirious smile. It was for him - it was  _that_ smile. Aang swirled a pinky to entice a cool blow of air over the sting on her arm.

 _I guess you’re here, too,_ he thought fondly, relief filtering into a tentative smile of his own, just as Katara asked, “Where am I?”

-

Where  _was_ he? He hardly recognised these noiseless streets. He knew it was a public holiday, but did all of Ba Sing Se fall silent in the day since they’d come up to meet with the King? Gingerly, he stepped into the store, feeling like an intruder. 

“Uhm, excuse me. Excuse me, do you have…” Zuko opened his palm to scrutinise the crumpled scrap of notepaper with Aang’s scrawl on it. “Bitter… bitter snail oil? A quarter ounce-” 

“Fire Lord Zuko!” exclaimed the young storekeeper, by way of answer. And it was all the answer he got before the boy dropped his gargantuan sack of dried - ginseng root? - and scuttled off. The door to the inner quarters of the shop swung with a noisy creak, before slamming hard behind him. Zuko and the dust puffed in his wake. 

Zuko sighed, glancing about. That was... what was it? The third shop? And this time he wasn’t even lucky enough to actually confirm that they didn’t have what he was looking for here. Aang had said two hours, or their best hope would be an arm amputation and an antidote ten times rarer than this one.

If that was possible, Zuko thought ruefully. 

Then again, Aang hadn’t been sure. He said he remembered Katara saying once that bitter snake oil was the best general antidote to toxins in arid places, and to dart scorpions in particular, but neither he nor the books the Royal staff found them were certain about the timing. King Kuei’s doctor was on leave for the weekend. 

In any case, Zuko had sprinted off - the stammering protests of the staff and his own guard faded by the time he could see the wall of the Inner Ring. Something in Aang sharpened the minute Kuei’s runaway scorpion had stung Katara, and he realised soon he had caught it too; was being sped into action before he knew it, as if he was on the string of some neurotic puppetmaster. 

Zuko’s eye caught the dusty signboard some way down the steep curve of the lane. The paint was peeling but he could still recognise the distinct colour of the characters. 

An apothecary. He wiped his brow and leapt down the lane.

Five minutes later, he was out on the street again, still empty handed. Only sweet snake oil in there, which sounded more like a poison than an antidote to him. Who knew, though?

That scorpion just had to go for Katara, of all people. If it were anyone but her, they would probably be back lazing in the gardens already as if nothing had happened. Zuko didn’t know a thing about medicinal herbs. Firecress and burnt cumin, that was the extent of it. He had a nurse once who poured some hot potion of it down his throat, and would have topped it off with a solid kick to the backside if he wasn’t the Fire Prince. Nothing like Katara. Well, maybe a bit.

There was that time he caught a chill in Daoshu and was handed some turmeric concoction. He remembered walking behind Aang and Katara with it cupped in his hands, their evening shadows enclosing him, providing just as much succour. Maybe bitter snake oil wasn’t even a thing, and Katara would be laughing at them if she were conscious. He couldn’t help but think of that if, and it settled his stomach like some medicine of its own. Zuko knew without knowing it that Aang was thinking the same as he waited.

He wouldn’t keep him waiting. With the paper in his balled fist, he sped on.

-

It was hot, and bedsitting was definitely not a strength of Aang’s, even when Katara was the one in the bed. He was dozing along with her, just as delirious now, the heat propelling slow mirages across his line of vision along with the floaters while he gazed out through the window. He saw the pond from this morning, the still water now swirling. The koi with its cavernous mouth. He saw Zuko coming over the brow of the hill. 

Wait.

He jerked awake and sprang to the window.

-

Her vision swam, occluded by strange spots, flitting in and away whenever she ventured to focus, like the fantailed goldfish she was watching in King Kuei’s pond. That was a memory of indeterminable origin, but it definitely was something that had happened. Was it this morning? Yesterday? Katara couldn’t tell. 

“...Aang?” 

She still couldn’t see, but she was quite sure that the scent of Aang was about. Whatever else she could vaguely sense felt starkly alien, including her own body. She thought she saw a scrap of orange light, or maybe the flash of Aang’s robes. 

“Zuko, I think it’s working!”

Something bolted up on her other side, and in a flash Zuko’s arm was around her shoulders. Her eyes opened to a clearing vision. Aang held her forearm in his hand, and it was full of a strange thrum. Gently, he moved his hand into hers and bent to kiss her forehead. Zuko kissed her temple, a clumsy moment where their knocking heads blocked Katara’s vision.

“What’s going on?” she said, feeling pleasantly light under their joint attention.

“You were stung by the King’s dart scorpion.”

“But Aang got the sting out.”

“And Zuko found the antidote.”

She looked between them, their now joined hands on her coverlet. Eyes bright and furrowed, a word away from cooing all over her again. She smiled.

A dart scorpion, eh? She had half a mind to thank it for its service.


End file.
